The purpose of the proposed research is to continue a longitudinal investigation of two independent cohorts of children who had been selected at either 21 or 31 months to be extreme for display of either inhibited or uninhibited behavior to the unfamiliar. In the first part of the research the children in the two cohorts will be seen at seven-and-a-half years of age. The children will be observed in a school setting, as well as in a laboratory context, to evaluate the degree to which the behaviors indicative of the two categories and the physiological signs of sympathetic arousal have been preserved since the last evaluations. The research will also determine if inhibited and uninhibited children show differential attention to figures symbolic of their personal style. It will also evaluate the degree of similarity between each parent and child on physiological variables that include perturbation of the voice, pupillary dilation, and heart rate gathered prior to, during, and after mild cognitive stress. A second study will evaluate the behavioral and physiological profiles of a group of four-year-old children who had been seen at 14 and 20 months, but who were unselected for inhibition and lack of inhibition. The profile of this group will be compared with that provided by children in the first study who had been selected to belong to the two extreme categories. A final study will test the hypothesis that extreme constipation, irritability, sleeplessness, and allergies in the first six months of life are predictive of inhibition, and their absence predictive of lack of inhibition, when the children are 21 months of age. The research should provide significant information for psychiatrists, psychologists, and other mental health professionals concerned with the etiology of phobias in children as well as panic reactions in adults.